[Note: The goal of this is not to donate more, it is to open Google Play on one of the donation pages, and then cancel.]
Go to Settings => Bonus features => Get bonus features.
Now choose a sum, for example $2 (just not the same amount you donated the previous time).
Click ‘Google Play’, and the Google Play window will open.
Now, don’t go through with the donation. Just make sure Google Play opened, and go as far as you can without actually paying.
Then cancel, and hopefully Google Play will have noticed that you already bought the bonus features.
If this doesn’t work, don’t hesitate to contact me on my e-mail or through the forums.